The KOOS-12 shortform shows no ceiling effect, good responsiveness and construct validity compared to standard outcome measures after total knee arthroplasty

Knee Surg Sports Traumatol Arthrosc. 2021 Feb;29(2):608-615. doi: 10.1007/s00167-020-05904-x. Epub 2020 Apr 16.


Purpose: To investigate the validity, responsiveness and ceiling effect of the recently introduced KOOS-12 and compare its performance to the KOOS, OKS, WOMAC and UCLA activity scales.

Methods: Patients from an independent multicentre study examining a medially stabilized knee system prospectively completed the KOOS, OKS, WOMAC and UCLA preoperatively and at 1 year postoperatively. KOOS-12 scores were calculated from the full length KOOS data. Construct validity was assessed using Spearman's correlation analysis. The ceiling effect was evaluated by calculating the percentage of patients with a maximum score. If the percentage exceeded 15%, a ceiling effect was considered to be present. Responsiveness was evaluated by performing paired t tests on the changes in measures and calculation of Cohen's d.

Results: A ceiling effect was present for the KOOS Pain, ADL and QoL subscales and the KOOS-JR at 1 year postoperatively. No ceiling effect was observed for the KOOS-12. Correlation of the KOOS-12 was low (0.3 < r < 0.5) with the UCLA, moderate (0.5 < r < 0.7) with the KOOS symptoms, sports and WOMAC stiffness subscales and high (r > 0.7) with all other scores and subscales. Effect size of the UCLA activity scale was moderate (Cohen's d 0.2-0.8) whereas effect sizes of all other outcome measures were large (d > 0.8).

Conclusion: The KOOS-12 does not exhibit a ceiling effect, has good convergent construct validity and is responsive to changes in pain, function, QoL and knee impact between preoperatively and 1 year postoperatively.

Level of evidence: Diagnostic level III.

Keywords: KOOS; KOOS-12; Osteoarthritis; Patient reported outcome measures; TKA.

Publication types

  • Multicenter Study

MeSH terms

  • Activities of Daily Living
  • Adult
  • Aged
  • Aged, 80 and over
  • Arthroplasty, Replacement, Knee*
  • Female
  • Humans
  • Knee Joint / surgery
  • Male
  • Middle Aged
  • Osteoarthritis, Knee / physiopathology
  • Osteoarthritis, Knee / surgery*
  • Pain Measurement
  • Patient Reported Outcome Measures*
  • Predictive Value of Tests
  • Quality of Life
  • Reference Standards
  • Reproducibility of Results
  • Treatment Outcome